For claims in the tort of negligence, the claimant must show that the defendant caused them a loss. The Courts have defined the test for causation, which is split into factual and legal causation. They have also needed to determine the meaning of ‘loss’.
The first case summaries involve questions of factual causation, which usually requires an application of the ‘but-for’ test. Where there has been issues of evidence and proof, the Courts have applied a different test looking at the contribution to the risk of damage or harm.
The next set of summaries concern the test for legal causation: proving the defendant in law caused the loss. The Courts have to decide whether an intervening event has broken the chain of causation. This is to decide whether the defendant is responsible for the claimant’s loss.
The final cases concern the meaning of ‘loss’.
1 – Factual Causation
The Courts usually apply the ‘but-for’ test to determine whether the act of the defendant factually ‘caused’ the claimant’s loss. If the loss would not have occurred ‘but-for’ the defendant’s actions, the Courts will say as a matter of fact that the defendant caused the loss.
Barnett v Chelsea and Kensington Hospital Management Committee 
Barnett demonstrates that the defendant must cause the loss, and it is for the claimant to show this. In Barnett, the claim was dismissed because, even though the doctor was negligent, on the balance of probability the doctor’s failure to take reasonable care had not caused the defendant’s death.
For successive tortious events, the second defendant is only liable for any extra damage they cause.
Performance Cars Ltd v Abraham 
Performance Cars Ltd v Abraham raised a novel point concerning successive events. Where two events cause the same harm which requires the same cost of repair, the second defendant can not be said to have caused this loss. The second defendant is only liable for any extra damage caused.
The House of Lords approved the decision in Performance Cars Ltd v Abraham. Where two persons do successive, separate acts causing the same loss, the second person is not liable for that loss. The second defendant will only be liable for any extra damage caused. Jobling v Associated Dairies 
In Jobling v Associated Dairies, the House of Lords reaffirmed the ‘vicissitudes’ principle to reduced the damages award where a second, natural event which would have occurred anyway overtook the claimant’s initial injury.
Exceptions to the but-for test
In some cases, particularly where there is insufficient evidence to determine what was the cause of an injury, the Courts have adopted a lower standard of test for factual causation.
Wardlaw v Bonnington Castings Ltd 
In Bonnington Castings, the House of Lords held the defendant was liable to the full extent for the claimant’s harm where their negligence was one of a number of sources of the damage but materially contributed to the injury.
In Holtby, the Court of Appeal concluded, following Bonnington Castings, that the defendant did factually cause the damage because they materially contributed to it. However, unlike in Bonnington Castings only held the defendant liable to the extent of their contribution. McGhee v National Coal Board 
In Holtby, the Court of Appeal concluded, following Bonnington Castings, that the defendant did factually cause the damage because they materially contributed to it. However, unlike in Bonnington Castings only held the defendant liable to the extent of their contribution. Fairchild v Glenhaven Funeral Services 
In Fairchild v Glenhaven Funeral Services, the HL approved the judgement in McGhee v National Coal Board. This means that in certain cases it is sufficient for the claimant to show the defendant materially contributed to the risk of harm. This principle was extended in Fairchild to include cases where a claimant can show that multiple claimants contributed to their harm, although can’t show with certainty which defendant was the but-for cause of the harm.
2 – Legal Causation
Intervening acts, or novus actus interveniens, can break the chain of causation between the defendant and the victim. Whilst factually they might be a cause for the loss, legally they are not said to have caused the loss.
Intervening natural events
Carslogie Steamship Co v Royal Norwegian Government 
In Carslogie, the House of Lords concluded claimants owe no damages in the tort of negligence where a subsequent natural event means the claimant suffered no further loss.
Intervening events by a third party
The Oropesa 
The Oropesa is an example where the subsequent act of another person did not break the chain of causation. It highlights that a person is still the legal cause for loss even when it occurs due to a person’s response to a negligent act.
Knightley v Johns 
Knightley v Johns clarified the law on ‘novus actus interveniens’ in the tort of negligence. It’s an example where subsequent acts by a third party broke the chain of causation between an act and injury.
Topp v London Country Bus 
Topp v London Country Bus is an example of a case where the act of a third party likely broke the chain of causation between the defendant and the victim.
Stansbie v Troman 
In Stansbie v Troman, due to the specific duty of care owed by the defendant the intervening act of a third party did not break the chain of causation. The breach of their duty made them directly responsible for the loss.
Intervening events by the claimant
Haynes v Harwood 
Haynes v Harwood is an example of a case where the claimant’s own act did not constitute a novus actus interveniens.
McKew v Holland 
McKew v Holland makes clear that the act of the claimant themselves can constitute a novus actus interveniens. This will be the case where the claimant acts unreasonably.